The word you're referring to is lieutenant, which is a military rank. Both Canadians and Americans pronounce it the same way: "loo-tenant".
There's a good chance you're thinking of the word "leftenant", which is a mispronunciation that is not used by Canadians or Americans. This mispronunciation likely stems from the fact that the word "lieutenant" shares the same initial sounds as the word "left," leading some people to mispronounce it.
So, to be clear: both Canadians and Americans pronounce "lieutenant" the same way, and the mispronunciation "leftenant" is not a common occurrence.